The network, which consists of Princess Margaret Hospital, Toronto General Hospital, Toronto Western Hospital and a number of rehabilitation sites, could not immediately say how long the review would take or when it would be reconnected to the broader system.

The problem — first reported by CTV News — came to light when a patient found results in his file for tests he had not taken.

The hospital network says errors have been found in four patient records and is isolated to its system.

The privacy breach has been reported to Ontario's Information and Privacy Commission.